Andre Agassi believes it is almost impossible for any player to take banned drugs and not get caught.
Andre Agassi was tested for drugs 20 times last year
The American, who is on the ATP's drug task force, said the sport's rigorous testing system would catch cheats.
"I don't know how you could do it for a short time much less how you would work it long term. I don't know how you'd pull it off," said Agassi.
He added that he no longer takes any nutritional supplements because he cannot be certain of the content.
Agassi, who is playing at the Nasdaq-100 Open in Florida this week, cited the number of times that he, world number one Roger Federer and Andy Roddick had been tested in the past year.
"I got tested 20 times last year, Federer 23 times and Andy 20 - we test so extensively that we have absolutely removed the possibility of somebody taking drugs to obtain a strategic advantage," said Agassi.
"We're tested all year long plus three out of competition tests. We have done everything to remove the possibility of someone taking advantage of drugs."